The ratings of all electrical equipment’s are all rated in KVA or Kilo Volt Amp. But the practical use is in KW. We can say it also that electrical equipment’s are rated in apparent power (KVA or VA) other then active power (KW or W).
Electrical equipment’s rated in KVA- the main reason
The trend of electrical rating in terms of VA(volt amp), KVA(kilo volt amp), MVA(mega volt amp) is due to the variation in the consumer side. In consumer or user side the electrical parameters are so varieties that a manufacturer can not cope of to all these variation. So the safe side is to rate the equipment in KVA.
The main criteria of the consumer side is variation in power factor– you can not predict it. And KVA rating has no terms or influence of power factor as it is the direct multiplication of voltage and current. On the other hand the kw is calculated by power factor which a manufacturer can not predict.
With KVA rating we can get the rated value of voltage and current. Say a small motor rated as 2KVA, we can get that its maximum current is 5amp with 400volt.Say a high capacity power plant alternator is rated by 12MVA , 0.80 power factor. We can get the MW value with simple calculation (12*0.80=9.6) that is 9MW. So we can get it that the KVA rating is not fully sufficient, we need the power factor also if it is applicable.